This proposal responds to RFA-AG-13-009 (Secondary Analyses and Archiving of Social and Behavioral Datasets in Aging), one goal of which is archiving and dissemination of data sets to enable secondary analysis. The primary objective is to extend our prior work in applying new documentation technology to MIDUS (Midlife in the United States), a national longitudinal study of approximately 10,000 Americans designed to study aging as an integrated biopsychosocial process. We will employ a technological metadata standard called the Data Documentation Initiative (DDI) to construct enhanced electronic codebooks for all MIDUS projects. Prior work applied DDI (2.1) to MIDUS codebooks, which were delivered to ICPSR, as well as used to create a searchable online repository. Upgrading all MIDUS codebooks to a more advanced version of DDI (3.2) will facilitate identification and harmonization of similar MIDUS variables, as well as enhance our online repository with a data extract function that will accomplish something unprecedented: the ability to obtain customized cross-project downloads of harmonized MIDUS data that are DDI-compliant. So doing will greatly facilitate efficient and effective public use of the large longitudinal and multi-disciplinary datasets that comprise the MIDUS study. DDI is based on a powerful language called eXtensible Markup Language (XML), a web-based data-publishing standard that is similar to HTML, but more powerful. XML allows data published on the web to be highly structured and interactive. Its main advantage is that it is machine-readable and in a format specifically designed to describe data. The latest version of DDI (3.2) contains nearly 900 new and revised tags and is designed to provide more efficient documentation of longitudinal and other complex hierarchical data structures. The specific aims of this proposal are: (1) to apply the DDI (3.2) metadata standard to all MIDUS-related data, upgrading M1 and M2 DDI (2.1) codebooks, and creating new codebooks from recently funded data collection efforts (including a Refresher cohort (national and Milwaukee-specific samples), a third wave of the original MIDUS sample (M3), and a second wave from the Japanese version of MIDUS called Midlife in Japan (MIDJA)); and (2) to integrate the DDI materials produced by Aim #1 into a searchable online repository from which researchers can create customized MIDUS datasets of internally harmonized variables. Accomplishing these aims will produce a DDI repository that performs variable searches across different MIDUS project datasets, identifies related variables along with their full metadata, enables custom data extracts of selected variables, and provides custom codebooks that contain information, procedures, and algorithms for their harmonization. These goals will be accomplished over a two-year period, following the sequential schedule for completion of data collection for the Refresher, M3 and MIDJA.